Unit testing in xcode 8 with swift

Unit Testing in Xcode 8.3.2
with Swift3
Allan Shih

Agenda
● What is Unit Testing?
● Unit Testing in Xcode
● Create a Unit Testing class
● Write a Unit Testing class
● Test Asynchronous Operations
● Faking Objects and Interactions
● Demo
● Reference

What is Unit Testing?
● Unit testing, a testing technique using which individual
modules are tested to determine if there are any issues
by the developer himself.
● It is concerned with functional correctness of the
standalone modules.

Unit Testing - Advantages
● Reduces Defects in the Newly developed features
● Reduces bugs when changing the existing functionality.
● Reduces Cost of Testing as defects are captured in very
early phase.
● Improves design and allows better refactoring of code.
● Unit Tests, when integrated with build gives the quality
of the build as well.

Unit Tests Main Properties
● Independent
○ Running a Unit Test should not affect another Unit Test run. Execution
order is not important.
● Fast
○ A test which takes several seconds to run is not a Unit Test and
probably needs a refactor.
● Isolated
○ Unit Test should not depend on external systems. They need to know
their collaborators answers.

Create a project with Unit Tests

Creating a Unit Test Target in an existing project
1. Click the test navigator
2. Click the + button
3. Select “New Unit Test
Target”
4. Create a Unit Test target

Build Settings > Deployment > iOS Deployment Target

Update CocoaPods
● Update a Podfile, and add test target dependencies:
● Run $ pod update in project directory.
● Open App.xcworkspace and build.
target 'ThingMakerMvc' do
use_frameworks!
pod 'Alamofire', '~> 4.3'
target 'ThingMakerMvcTests' do
inherit! :search_paths
end
end

Run the test class
1. ProductTest or Command-U. This actually runs all test
classes.
2. Click the arrow button in the test navigator.
3. Click the diamond button in the gutter.

Unit Test Class Structure
● Class Setup/TearDown
○ Executed once when the Unit Test class is initialized, not for every test
in the class. Useful to avoid test code duplication at class level.
● Test Setup/TearDown
○ Executed once before and after each executed Unit Test. Useful to
avoid test code duplication at test level.
● Test Methods
○ The Unit Test implementation itself. Here is where the test run and
validations happens.

Test Setup / Tear Down Example
@available(iOS 9.0, *) UIViewController.loadViewIfNeeded()

Tests Naming
● Use descriptive test names. It will provide quick
feedback when test fails.
● Choose names which in few words says:
○ Method under testing
○ Condition under testing
○ Expected result / behavior

Tests Naming Example
● Good examples
○ testSyncLullabyList_withLullabyManager_return3LullabyItems()
○ testSyncStationList_withIHeartRadioApi_return6StationItems()
● Bad examples
○ testExample1()
○ testExample2()
○ testExample3()

Test Method Organization
● Arrange / Setup
○ Prepare all needed objects/dependencies for test execution.
● Act / Test
○ Test itself it performed, calling one specific method in the system
under testing.
● Assert / Verify
○ Method result/behavior verification is performed at the end, using test
asserts.

Tests Verification Types
● Return Value / State Verification
○ Verify the result returned for the method under test, no matter which
interactions with other objects has been made. Useful and preferred
verification in most cases.
● Behavior Verification
○ Verify that all tested method interactions among other collaboration
objects are the expected one (generally done using mocks). Useful for
some cases where interactions are important (for example a cache
implementation).

Return Value Verification Example

XCTAssert Family in XCode 8.3.2
XCTAssert Family Description
XCTAssert Asserts that an expression is true.
XCTAssertTrue Asserts that an expression is true.
XCTAssertFalse Asserts that an expression is false.
XCTAssertNil Asserts that an expression is nil.
XCTAssertNotNil Asserts that an expression is not nil.
XCTAssertEqual Asserts that two expressions have the same value.
XCTAssertEqualObjects Asserts that two objects are considered equal.

XCTAssertNotEqual Asserts that two expressions do not have the same value.
XCTAssertNotEqualObjects Asserts that an expression is true.
XCTAssertGreaterThan Asserts that the value of one expression is greater than
another.
XCTAssertGreaterThanOrEqual Asserts that the value of one expression is greater than or
equal to another.
XCTAssertLessThan Asserts that the value of one expression is less than
another.
XCTAssertLessThanOrEqual Asserts that the value of one expression is less than or
equal to another.

XCTAssertThrowsError Asserts that an expression throws an error.
XCTAssertNoThrow Asserts that an expression does not throw an
NSException.

Demo
Write a Unit Testing class

XCTestExpectation
● Define an expectation with a meaningful description.
● Go on with the test setup and exercise phases, calling
the asynchronous method and fulfilling the expectation
at the end of the callback closure.
● Make the test runner wait for you expectation to be
fulfilled, so that the asynchronous operations can be
completed and you assertions verified.

Demo
Test Asynchronous Operations

Asynchronous Tests Problem
● Most apps interact with system or library objects, but
you don’t control these objects.
● Tests that interact with these objects can be slow and
unrepeatable.
● The singletons made our class hard to test.

Dependency Injection
● Extract and Override
○ Create a testing subclass and override the testing method.
● Method Injection
○ Pass a dependency object during a method.
● Property Injection
○ An internal or public property can be modified or replaced.
● Constructor Injection
○ Pass a dependency object during the constructor.

Sync Lullaby with LullabyManager

Extract and Override Example - Create a Mock Class

Extract and Override Example - Verifying Lullaby List

Method Injection Example - Create a property that holds a reference

Method Injection Example - Dependency object can be replaced

Method Injection Example - Use a mock LullabyManager object

Property Injection Example - Create a internal or public property

Property Injection Example - Use a mock LullabyManager object

Constructor Injection Example - Default Constructor

Constructor Injection Example - Dependency object can be replaced

Constructor Injection Example - Use a mock LullabyManager object

Types of Test Doubles
● Stub
○ Fakes a response to method calls of an object.
● Mock
○ Let you check if a method call is performed or if a property is
set.

Mock Example - Create a Mock Class

Reference
● About Testing with Xcode - Apple
● Unit Testing in Xcode 7 with Swift - AppCoda
● iOS Unit Testing and UI Testing Tutorial - RayWenderlich
● Test Doubles: Mocks, Stubs, and More - objc
● MCE 2014: Jon Reid - Test Driven Development for iOS
● Waiting in XCTest

Unit testing in xcode 8 with swift

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